Re: Page 76 of OCaml by John Whitington ???

Part of the problem is that the "reference solution" is incomprehensible.  Here's how I did it:

let pack li =
  let rec grab_block li ac =
    (* Grab a block of equal elements from li and put them into ac.
       Return the pair (li,ac). *)
    match li with
      | [] -> ([],ac)
      | x::tail ->
    if ac=[] || x = List.hd ac then grab_block tail (x::ac)
    else (li, ac)
  in
  let rec loop li ac = if li = [] then List.rev ac else
      let (rest,bl) = grab_block li [] in
      loop rest (bl::ac)
  in
  loop li []

I think this is much easier to understand, and just as efficient.

---DS